Method for manufacturing an optical filter for a stereoscopic image display device

ABSTRACT

The present invention relates to a method for manufacturing an optical filter for a three-dimensional image display device, which forms an alignment layer having different orientating directions along a fine region via a one-time continuous optical orientation process. The method comprising: forming a polymer layer on a substrate; a photo-orienting step comprising positioning a pattern mask above the polymer layer, the pattern mask having alternating light transmission regions and light shield regions arranged in both horizontal and a vertical directions to selectively transmit different polarized light, positioning a polarizer above the pattern mask where the polarizer has two distinguishable regions that transmit different polarized light, and downwardly irradiating UV light onto the polymer layer from above the polarizer, thereby forming an alignment layer having different orientating directions in fine regions of the polymer layer; and forming a retardation layer on the orientation layer. The alignment layer in which the fine regions with different orientating directions are formed alternately and continuously is obtained via a one-time continuous photo-orientation process. Therefore, the photo-orientation process and the method for manufacturing the optical filter are simplified in comparison with the conventional art. As a result, the process yield and productivity in the manufacturing of an optical filter for a 3D image display device are improved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing an optical filter for a three-dimensional image display device, and more particularly, to a method for manufacturing an optical filter for a three-dimensional image display device, which forms an alignment layer having different orientating directions along a fine region via a one-time continuous optical orientation process.

2. Description of the Related Art

Three-dimensional (3D) image display technology is technology that displays a 3D image as if the object actually exists in 3D space. 3D image display technology is expected to lead the next generation of display devices as a new concept in realistic image display technology improving on the level of planar visuals.

A 3D effect is realized via a procedure in which the left and right images of an object, perceived by the left and right eyes, are processed by the brain. That is, since a person's eyes are spaced apart by about 65 mm, they see images in two slightly different directions. At this time, a 3D effect is realized due to the optical phenomenon of binocular disparity.

In order to display a 3D image, a 3D image display device uses a method of displaying stereoscopic images (3D image), that are slightly different images seen by an observer's respective left and right eyes. Such stereoscopic images can be displayed by way of the use of an eyeglasses method and an eyeglasses-free method. The methods for viewing a 3D image without wearing glasses include a parallax barrier method and a lenticular lens method. The parallax barrier method implements binocular disparity through a light shield layer having a structure in which barriers are regularly attached to the front or rear surface of a display panel. The lenticular lens method implements binocular disparity by using a small and regular semicylindrical lens called a lenticular lens. The two methods are advantageous in that glasses are not required; however, they are disadvantageous in that the effective viewing angle in which to obtain a 3D effect is significantly narrow, allowing only a single person to view a 3D image, and it is difficult to convert a 2D image into a 3D image.

The methods of viewing a 3D image while wearing glasses can be roughly divided into a shutter glasses method and a polarized glasses method. According to the shutter glasses method, the left-eye image and the right-eye image as displayed on a screen are alternately transmitted to each eye by the shutter glasses. An observer is able to separately recognize the left-eye image and the right-eye images alternately displayed on the screen due to the shutter glasses, and a 3D effect is obtained as the observer processes the two different images within his or her brain. However, the 3D display device using the shutter glasses method is disadvantageous in that the use of the shutter glasses increase the price of the product and an observer is directly exposed to electromagnetic waves generated by the driving of the shutter glasses.

According to the polarized glasses method, a patterned polarizer is mounted on an image display device. An observer experiences a 3D effect as a left-eye image and a right-eye image, having different polarization characteristics, are transmitted through the polarized glasses. The polarized glasses method is disadvantageous in that an observer must wear the polarized glasses, but is advantageous in that limitations on the viewing angle are small and the manufacturing thereof is easy.

The 3D image display device using the polarized glasses method may further include an optical film (optical filter) on the front surface of a screen display unit of a display device. As disclosed in U.S. Pat. No. 5,327,285, an optical film used in a 3D display device using the polarized glasses method, an optical film in which the right-eye image display unit and the left-eye image display unit are alternately disposed parallel to each other, is manufactured by coating a photoresist on a polarizing film in which a tri acetyl cellulose (TAC) film and an iodized stretched poly vinyl alcohol (PVA) film are laminated, exposing a predetermined portion, and by treating the exposed portion with a potassium hydroxide solution so that the function of phase difference of the predetermined portion is removed. Meanwhile, Korean Patent Application No. 2000-87186 discloses a method for manufacturing a 3D image display device. According to this patent application, a transparent substrate is coated with a birefringent material, and the birefringent material is subsequently partially exposed to light through a mask, thereby obtaining an optical filter (optical film) having portions in which chiral characteristics are modulated and portions in which original chiral characteristics are maintained, both of which are alternately arranged.

However, the manufacturing method disclosed in U.S. Pat. No. 5,327,285 is problematic in that it entails a complicated manufacturing step due to chemical etching, has high manufacturing costs, and has low productivity. The polarizing filter manufacturing method disclosed in Korean Patent Application No. 2000-0087186 is problematic in that it is actually somewhat difficult to control the chiral characteristics of the retarding material by using the intensity of light, resulting in low yield and instability according to temperature.

Therefore, there is a need for a method in which an optical filter for a 3D image display device with excellent process efficiency and productivity can be manufactured.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method for manufacturing an optical filter for a 3D image display device, which is capable of improving productivity and process efficiency by simplifying its manufacturing process.

An aspect of the present invention also provides a method for manufacturing an optical filter for a 3D image display device, which forms an alignment layer have different orientating directions in a fine region, via a single continuous optical orientation process.

Accordingly, an aspect of the present invention provides a method for manufacturing an optical filter for a 3D image display device, the method comprising: forming a polymer layer on a substrate; a photo-orienting step comprising positioning a pattern mask above the polymer layer, the pattern mask having alternating light transmission regions and light shield regions arranged in both horizontal and a vertical directions to selectively transmit different polarized light, positioning a polarizer above the pattern mask where the polarizer has two distinguishable regions transmitting different polarized light, and downwardly irradiating UV light onto the polymer layer from above the polarizer, thereby forming an alignment layer having different orientating directions in fine regions of the polymer layer; and forming a retardation layer on the orientation layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more clearly understood from the following detailed description viewed in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a photo-orientation step in a method for manufacturing an optical filter according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating an implementation example of a pattern mask having a two-stage pattern which is usable in the photo-orientation step in the method for manufacturing the optical filter according to the embodiment of the present invention;

FIG. 3 is a diagram illustrating an implementation example of a pattern mask having a one-stage pattern which is usable in the photo-orientation process in the method for manufacturing the optical filter according to the embodiment of the present invention; and

FIG. 4 is a diagram illustrating the use of two sheets of a pattern mask having the one-stage pattern of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Reference numerals in the drawings denote like elements, and thus their description will be omitted.

An embodiment of the present invention provides a method for manufacturing an optical filter, which is used in a 3D image display device using the polarized glasses method, having a simpler process and greater process efficiency, as compared with the conventional art. Different orientations are assigned to a fine region of a polymer layer via one-time continuous light irradiation.

In the method according to the embodiment of the present invention, a polymer layer is formed on a substrate, and different polarized light is irradiated onto a region of the polymer layer via a one-time continuous optical orientation step. In this way, different orientations are assigned to the fine region of the polymer layer. Then, an optical filter is manufactured by forming a retardation layer (a liquid crystal layer) on the polymer layer (alignment layer) having different orientations, depending on the region. FIG. 1 illustrates a method for manufacturing an optical filter according to an embodiment of the present invention, specifically, a process for forming the polymer orientation layer having different orientating directions, depending on the fine regions of the polymer layer.

The substrate for the polymer alignment layer may include, but is not limited to, any substrate generally used in the art to which the invention pertains. For example, the substrate may include a tri acetyl cellulose substrate, a poly ethylene terephthalate substrate, a poly methyl methacrylate substrate, a polycarbonate substrate, a polyethylene substrate, a cycloolefin polymer, such as a norbornene derivative substrate, a polyvinyl alcohol substrate, a diacetylcellulose substrate, or a glass substrate.

As illustrated in FIG. 1, a polymer layer 2 is formed on a substrate 1. The polymer layer 2 is a polymer resin whose orientation is assigned by light irradiation. The polymer layer 2 may be formed by any resin which is commonly used in the forming of a polymer alignment layer. The polymer layer may be made of at least one polymer resin selected from the group consisting of polyamide, polyimide, polyvinyl alcohol, polyamic acid, and poly cinnamate. However, the present invention is not limited thereto.

An alignment layer is obtained by irradiating polarized light onto the polymer layer 2 in order to assign orientations thereto. The optical filter for the 3D image display device must have different orientations on a predetermined region of the polymer layer in order to project images with different polarization characteristics. Therefore, the optical orientation step for forming the alignment layer with different orientations, depending on the region, is performed by using a mask having a pattern through which different polarized light can be selectively transmitted, depending on the region of the polymer layer. Specifically, the pattern mask has light transmission regions and light shield regions that alternate with each other in both a horizontal direction and a vertical direction, so that different polarized light may be selectively transmitted. One or more sheets of the pattern mask may be used depending on the pattern to be formed on the mask.

FIG. 2 illustrates an example of a pattern mask which may be used in the method according to the embodiment of the present invention. The pattern mask of FIG. 2 includes a first stage pattern and a second stage pattern. The first stage pattern has alternating light transmission regions and light shield regions that alternate with each other in a horizontal direction. The second stage pattern has light shield regions and light transmission regions located below the light transmission regions and the light shield regions of the first stage pattern, respectively. Specifically, the light transmission regions and the light shield regions of the first stage pattern and the second stage pattern alternate with each other both in a horizontal direction and in a vertical direction. In the case of the pattern mask illustrated in FIG. 2, one sheet of the pattern mask having alternating light transmission regions and light shield regions in both a horizontal direction and a vertical direction is used. Thus, as illustrated in FIG. 1, the alignment layer having different orientating directions in a fine region of the polymer layer can be formed. If necessary, two or more sheets of the pattern mask illustrated in FIG. 2 may be used.

Furthermore, as illustrated in FIG. 3, two sheets of a pattern mask having alternating light transmission regions and light shield regions is used to provide the mask pattern as illustrated in FIG. 2. In this way, an alignment layer having different orientating directions in a fine region of the polymer layer may be formed. FIG. 4 illustrates a state in which two sheets of the pattern mask illustrated in FIG. 3 are arranged. That is, as illustrated in FIG. 4, the pattern mask of FIG. 3 may be used in such a manner that the light transmission regions and the light shield regions alternate in a vertical direction. If necessary, three or more sheets of the pattern mask illustrated in FIG. 3 may be used.

Although not limited thereto, for example, as illustrated in FIG. 1, the pattern mask 3 having the pattern of FIG. 2 or two sheets of the pattern mask 3 having the pattern of FIG. 3 are positioned above the polymer layer 2 as illustrated in FIG. 4. A UV polarizer 4 having two regions transmitting different polarized light is positioned above the pattern mask 3 parallel to the film progress direction. Then, while moving the polymer layer in the film progress direction of FIG. 1, UV light is irradiated downward from above the UV polarizer 4 through the UV polarizer and the pattern mask 3 to the polymer layer 2. Thus, different polarized UV light is selectively irradiated onto the first region and the second region of the polymer layer. Accordingly, an alignment layer, in which predetermined regions with different orientating directions are alternately formed, is obtained. More specifically, in the alignment layer illustrated in FIG. 1, the first region and the second region, in which polymer is aligned in different orientating directions, are alternately formed in a lengthwise direction.

A retardation layer is subsequently formed on the alignment layer. The phase retarding layer may be formed by coating and cross-linking photo-crosslinkable liquid crystal, more specifically, nematic liquid crystal. The nematic liquid crystal is a polymerizable reactive liquid crystal polymer. The nematic liquid crystal is polymerized with an adjacent liquid crystal monomer by light to thereby form a liquid crystal polymer. The nematic liquid crystal may include any kind of a nematic liquid crystal which is generally known as a material used to form a retardation layer in the arts to which the invention pertains. One or more kinds of materials having an acrylate group, which is polymerizable by photoreaction, may be used. Examples of the liquid crystal material having the acrylate group may include a low-molecular-weight liquid crystal exhibiting a nematic phase at room temperature or high temperature, such as cyano biphenyl-based acrylate, cyano phenyl cyclohexane-based acrylate, cyano phenyl ester-based acrylate, benzoic acid phenyl ester-based acrylate, phenyl pyrimidine-based acrylate, and a mixture thereof.

The photo-crosslinkable liquid crystal is coated onto the alignment layer in an isotropic material state and is then phase-transitioned to a liquid crystal by polymerization during drying and curing processes. Thus, the photo-crosslinkable liquid crystal is aligned in a specific direction (absorbance axis direction of the UV polarization direction) and its orientating direction is fixed. That is, since the optical axes of the nematic liquid crystal with the optical anisotropy on the alignment layer having different orientating directions, depending on the fine regions, are differently aligned depending on the regions where the polarization direction of light passing through the fine regions is differently controlled. Furthermore, the orientation of the liquid crystal is not changed in subsequent processes, even though another layer is laminated on the retardation layer.

In forming the retardation layer, the coating thickness of the photo-crosslinkable liquid crystal may be adjusted so that the retardation layer has an appropriate phase retarding value. Meanwhile, the retardation layer may be formed to have a phase difference value of a ½ wavelength in order for conversion to a linearly polarized light, and have a retardation value of a ¼ wavelength in order for conversion to circularly polarized light.

In 3D display device technology using the polarized glasses method, an optical filter manufactured by the method according to the embodiment of the present invention may be used.

In the method for manufacturing the optical filter according to the embodiment of the present invention, except for the formation of the alignment layer in which the fine regions (specifically, the first region and the second region) with different orientating directions due to the use of the specific mask and the polarizer having two regions transmitting different polarized light are alternately formed, the substrate, the polymer layer, the kind of liquid crystal, the materials used to form the polymer layer and the retardation layer, the forming method thereof, and the thickness of the polymer layer as well as the retardation layer are common in the art to which the invention pertains and may be selectively applied in order to exhibit desired optical characteristics, but the present invention is not limited thereto.

Hereinafter, the embodiment of the present invention will be described. The following embodiment is an exemplary implementation example which will help with understanding the present invention, but the present invention is not limited thereto.

As illustrated in FIG. 1, a poly cinnamate polymer layer 2 having a dry thickness of 1,000 Å was formed on a tri acetyl cellulose substrate 1 having a thickness of 80 μm.

The poly-cinnamate polymer layer 2 was formed by coating a polymer layer forming solution on the tri acetyl cellulose substrate 1, having a thickness of 80 μm to a dry thickness of 1,000 Å by using a roll coating method, and removing the solvent from the inside of the coating layer by heating at 80° C. for 2 minutes in an oven. At this time, the polymer layer forming solution was prepared by mixing a mixture of polynorbornene having a cinnamate group of a chemical formula 1 below (weight-average molecular weight (Mw)=150,000) and a acrylate monomer with a photoinitiator (Igacure 907) and dissolving the resulting compound in a cyclohexanone solvent so that the solid content of the polynorbornene became 2 wt %. Meanwhile, the weight ratio of polynorbornene:acrylate monomer:photoinitiator was 2:1:0.25. As the solvent, a cyclopentanone solvent instead of the cyclohexanone solvent may also be used.

Then, like the pattern mask illustrated in FIG. 2, a pattern mask 3 (100 mm×100 mm) was placed above the poly-cinnamate polymer layer 2. The pattern mask 3 has alternating light transmission regions and light shield regions that alternate with each other in both a horizontal direction and a vertical direction, and the width of the light transmission region is 500 μm.

In the pattern mask 3, the width of the light transmission region must be matched with the pixel interval of the display device in which the manufactured optical filter is to be used. For example, the width of the light transmission region may be an interval of about 300 μm for a monitor, and may be an interval of about 450 μm for a TV, but the present invention is not limited thereto. In the mask pattern, there is no special limitation on the length of the light transmission regions. Those skilled in the art can suitably adjust the length of the light transmission region in consideration of the amount of light necessary for orientation and convenience in photo-orientation.

Then, as illustrated in FIG. 1, a UV polarizer 4 having two regions transmitting different polarized light was positioned over the pattern mask 3 parallel to the film progress direction. Thereafter, UV light having an intensity of 300 mW/cm² was continuously irradiated downwards from above the UV polarizer 4 for 30 seconds, while substrate was moved at a speed of 3 m/min in the film progress direction of FIG. 1, thereby obtaining the orientation layer in which the first orientation region and the second orientation region having polymers aligned in different directions along a predetermined region of the poly cinnamate polymer layer 2 are alternately formed along a lengthwise direction of the polymer layer.

As the liquid crystal material, LC242™, commercially available from the BASF Company, was coated to have a dry thickness of about 1 μm, and the liquid crystal was cured by irradiating UV light having an intensity of 300 mW/cm² upon it for 10 seconds, thereby forming a retardation layer. As the liquid crystal material, Reactive Mesogen (RM) based materials may also be used. Since the retardation layer was formed on the alignment layer in which polymers were aligned in different orientating directions in the fine regions, the optical axes of the optical anisotropic material are differently aligned in the fine regions. As a result, an optical filter for a 3D image display device was obtained.

When light passes through the optical filter according to the embodiment of the present invention, in which the optical axes of the liquid crystal are differently aligned and fixed in the fine regions, the light polarization direction is differently controlled, depending on the transmission regions of the optical filter. Therefore, since the left-eye image and the right-eye image with different polarization characteristics as emitted through the polarization filter, are projected through the polarized glasses, the observer recognizes a 3D effect via the polarized glasses method.

In the method for manufacturing the optical filter for the 3D image display device, the pattern mask in which the light transmission region and the light shield region alternately intersect vertically and horizontally and the polarizer having two distinguishable regions transmitting different polarized light are used in order that different polarized light is selectively transmitted. Therefore, the fine regions of the polymer layer are alternately arranged in different orientating directions by the continuous photo-orientation process via one-time continuous light irradiation.

Therefore, a alignment layer in which the fine regions with different orientating directions are formed alternately and continuously is obtained. Since such an alignment layer is formed by a one-time continuous photo-orientation process, the photo-orientation process and the method for manufacturing the optical filter are simplified in comparison with the conventional art. As a result, the process yield and productivity in the manufacturing of the optical filter for the 3D image display device are improved.

While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A method for manufacturing an optical filter for a 3D image display device, the method comprising: forming a polymer layer on a substrate; photo-orientation comprising positioning a pattern mask above the polymer layer, the pattern mask having alternating light transmission regions and light shield regions both in horizontal and vertical directions to selectively transmit different polarized light, positioning a polarizer above the pattern mask where the polarizer has two distinguishable regions that transmit different polarized light, and downwardly irradiating UV light onto the polymer layer from above the polarizer, thereby forming an alignment layer having different orientating directions in fine regions of the polymer layer; and forming a retardation layer on the orientation layer.
 2. The method of claim 1, wherein the pattern mask comprises: a first stage pattern having alternating light transmission regions and light shield regions in a horizontal direction; a second stage pattern having light shield regions and light transmission regions located below the light transmission regions and the light shield regions of the first stage pattern, respectively, so that the alternating light transmission regions and the light shield regions of the first stage pattern and the second pattern alternate with each other in both a horizontal direction and a vertical direction.
 3. The method of claim 1, wherein the pattern mask is used so that two sheets of a pattern mask having a first stage pattern with alternating light transmission regions and light shield regions in a horizontal direction is positioned where light transmission regions and light shield regions of a first pattern mask and a second pattern mask alternate in a vertical direction.
 4. The method of claim 1, wherein the polymer layer comprises at least one selected from the group consisting of polyamide, polyimide, poly vinyl alcohol, polyamic acid, and poly cinnamate.
 5. The method of claim 1, wherein the retardation layer is formed of nematic liquid crystal.
 6. The method of claim 1, wherein the retardation layer is formed to have a retardation value of ½ wavelength or ¼ wavelength. 